RNNP report: Risk development for acute spills on the Norwegian continental shelf 2001-2010

During the period 2001–2010, there has been a significant reduction in the number of acute crude oil spills on the Norwegian continental shelf. The reduction was greatest during the first years of the period, while the number of spills following this remained stabile for several years. In 2010, the number has declined again, but it is too early to say whether this is the start of a further positive development.

The Petroleum Safety Authority Norway (PSA) monitors risk development in the petroleum activities in a number of ways. An important tool in this context is the mapping work within “Risk levels in Norwegian petroleum activities” – RNNP.

Since 2000, RNNP has been responsible for collecting extensive data material regarding accidents and undesirable incidents in the petroleum activities. In the beginning, the data was assessed to follow up the risk development for major accidents and personal injuries.

In 2009, work was started to utilise parts of this data material and parts of the Environment Web database in order to also monitor the risk development for acute spills on the Norwegian shelf. Risk in this connection means frequencies and volumes of acute spills. The actual and potential consequences of spills as regards environmental damage are not considered.

Development – actual spills
The RNNP data shows that the overall number of acute crude oil spills on the Norwegian shelf was more than halved from 2001 to 2004. After remaining nearly constant during the period from 2004-2009, the number declined further in 2010.

The figure below shows the total number of acute spills per facility year during the period 2001-2010.

There has been a considerable reduction in the number of acute oil spills per year in the North Sea. The reduction was greatest up to 2003, while the reduction in the last six years has been limited. There was an increase early in the 2000s in the Norwegian Sea, followed by a considerable reduction, and then a stabile level from 2004.

In addition to data regarding acute crude oil spills at sea, the report also includes data relating to acute spills of other oils (mainly hydraulic oil and diesel oil) and chemicals. After 2004, the volume of such spills per facility year has been greater in the Norwegian Sea than in the North Sea. In the Norwegian Sea, four major acute diesel oil spills have occurred during the period 2007-2010.

Development – near misses
The basis for the report is acute spills that occurred in the petroleum activities in the last ten years, but it also analyses incidents that could have led to acute spills if more barriers had failed.

The figure shows a three-year rolling average number of registered near misses that could have led to acute crude oil spills, normalised according to the number of facility years. A theoretic “statistically expected” discharge volume has been calculated in order to gain an indication of the degree of severity of the potential spills.

It emerges from the figure that the number of near misses that could have led to acute spills has declined in the ten-year period and that the number of such incidents per facility year in 2009 and 2010 are the lowest values in the period.